This invention relates to a steering system for an independent suspension, and more particularly, the invention relates to a so-called steer-by-wire steering system.
Commercial vehicles such as buses and trucks often incorporate unique steering systems. Buses and trucks must typically make very sharp turns which complicates the design of the steering systems. For example, a mechanical steering system typically includes a rack and pinion connected to a steering knuckle by cross tubes and tie rods. The rack and pinion steering system manipulates the steering knuckles in response to steering input from the steering wheel. Mechanical steering components must be packaged in the limited space available around the vehicle frame. Furthermore, packaging of the mechanical steering components may limit the maximum allowable turning angle due to lock up or binding of the steering components when turning the steering knuckles. That is, interference between the steering components and frame may prevent a desired turning angle from being achieved.
Packaging of mechanical steering systems may be further complicated when using independent suspension systems such as arrangements utilizing upper and lower control arms. To this end, so-called steer-by-wire systems have been incorporated to replace the mechanical steering components traditionally used. However, these steer-by-wire systems may be relatively complicated and may encounter some of the same packaging problems confronted with mechanical steering systems. For example, many steer-by-wire systems utilize hydraulic cylinders or numerous interrelated linkages coupled to the steering knuckle to effectuate a turn. Therefore, what is needed is a compact steer-by-wire system for an independent suspension.
The present invention provides a steering system for a vehicle including a frame. Upper and lower control arms have first end portions that are pivotally supported on the frame at first spaced apart connections. The control arms also each include second end portions that are pivotally connected to an intermediate support member at second spaced apart connections. A steer knuckle is pivotally supported by the intermediate support member at third spaced apart connections that define a king pin axis. A drive motor is mounted on the intermediate support member and is coupled to the steering knuckle to rotate the steering knuckle about the king pin axis relative to the intermediate support member. A gear set may also be used in conjunction with the drive motor and steering knuckle. The intermediate support member is constrained against forward and aft movement, but is permitted to move upward and downward with the control arms.
Accordingly, the above invention provides a compact steer-by-wire system for an independent suspension.